[unreadable] This proposal seeks funding for the acquisition of a hybrid quadrupole/trap-Fourier transform ion cyclotron esonance mass spectrometer equipped with a 12 Tesla superconductive magnet, electrospray ionization (ESI), electron capture dissociation (ECD), and infrared multiphoton dissociation (IRMPD). This configuration affords the state-of-the-art capabilities necessary to complete the high-resolution characterization of nucleic acids and their non-covalent and covalent adducts, which is at the core of the supported research projects. The participants have established programs aimed at advancing our understanding of infectious diseases and cancer by tackling fundamental questions concerning retroviral replication and packaging, drug resistance, and gene damage and repair. The proposed instrument will provide the basis for structural and functional investigations that would not be possible by traditional approaches used in structural biology and biochemistry. In particular, it will enable the implementation of structural probing, binding constants determination, kinetics analysis, and top-down characterization of biological substrates that are very susceptible to degradation (e.g., RNA and RNA-adducts), inherently labile (e.g., non-covalent complexes), and present in very low amounts (e.g., DNA-adducts). The resolving power afforded by the high magnetic field will be crucial for the analysis of the complex analyte mixtures obtained by treating nucleic acid substrates and protein-nucleic acids assemblies with footprinting reagents, bifunctional crosslinkers, biochemical probes, carcinogenic agents, nucleotide analogues, and candidate inhibitor ligands. The front- end of the hybrid will enable to control the number of ions admitted into the cell to improve resolution, dynamic range, and performance in tandem mass spectrometry. The combination of ECD and IRMPD will provide the ability to complete the unambiguous characterization of chemically-modified products and crosslinked heteroconjugates. In addition to the described projects lead by the primary users, the proposed instrument will support the work of many other biomedical investigators with a proven need for high- resolution mass spectrometry (secondary users). The anticipated service component will complement the activities of two distinct core facilities serving the University of Maryland Baltimore County (UMBC) campus and the University of Maryland at Baltimore (UMB) Greenebaum Cancer Center and Medical School. [unreadable] [unreadable] [unreadable] [unreadable]